Characterization of the variability in lysine content for normal and opaque2 maize endosperm

Endosperm lysine content is genetically variable in maize (Zea mays L.) germplasm, but its level is below the minimum dietary standard set by the FAO. Increasing the content of this essential amino acid in endosperm proteins depends on understanding the mechanisms regulating the synthesis and accumulation of lysine-rich proteins. In this study, we analyzed the variability for lysine and protein contents in maize endosperm. Amounts of total protein, zeins, and non-zeins measured by microKjeldahl, and lysine content, estimated by aminoacid analysis, were determined for 93 maize inbreds. Additionally, an ELISA was used to estimate the relative content of the protein synthesis factor EF-1 alpha in 20 selected genotypes. Considerable differences in lysine content were observed among normal and opaque2 genotypes, with the effect of the mutation being highly dependent on the genetic background. We detected a high correlation between the lysine content and the concentration of total non-zein proteins and EF-1 alpha. An assay for EF-1 alpha concentration may provide a simple and inexpensive method from breeding programs to select for improved protein quality.